Snap-acting mechanisms



Oct. 1, 1963 H. K. BuRcH ETAL SNAP-ACTING MEcHANsMs 6 Sheets-Sheet 1 Filed July 5, 1960 Oct. 1, 1963 H, K. BURcH ETAL SNAP-ACTING MECHANIsMs Filed July 5, 1960 6 Sheets-Sheet 2 Oct. 1, 1963 H. K. BURcH ETAL 3,105,885

SNAP-Acum MEcHANlsMs Filed July 5, 1960 6 Sheets-Sheet 3 Oct.- 1, 1963 H. K. BURcH ETAL SNAP-ACTING MECHANIsMs 6 Sheets-Sheet 4 Filed July 5, 1960 Oct. 1, 1963 H. K. BuRcH E'rAl.

SNAP-ACTING MECHANIsMs 6 Sheets-Sheet 5 Filed July 5. 1960 Oct. 1, 1963 6 Sheets-Sheet 6 Filed July 5, 1960 United States Patent 3,185,886 SNAP-ACTING MECHANISMS Hadley K. Burch, Ridgehury Road, RD. 1, Danbury, Conn., and Malcolm I. Parkhurst, 142 E. 150th St., New York, NX.

Filed July S, 196i), Ser. No. 40,845 Claims. (Cl. 20S-67) This invention relates to snap-acting devices, and in particular to snap acting devices of the over centering kind which are particularly adapted for miniturized versions of snap-acting switches.

It is well known that snap-acting devices may be made in the form of multi-legged members, with the stressing of one or more of said members creating internal stresses which result in imparting a generally dished shape to the member, with the result that when mechanically further stressed, the device will change shape or dish suddenly. While satisfactory for many uses and achieving a large measure of commercial success, such devices, when made in very small sizes, may become diicult to use, because of inherent criticality to dimensional tolerances. Also, when such devices are reduced to relatively small sizes, the amount of snap motion may not be very large. Thus, electrical snap-switches using such devices may not be entirely suitable for certain applications, in view of the resulting very small contact opening.

It is a general object ofthe present invention, therefore, to provide a new and improved snap-acting device, readily adaptable as an electrical snap-Switch or the mechanical motivating part of some other device.

Another object of the invention is to provide a new and improved snap-acting device especially adapted to the production of exceptionally small snap-switches.

It is a further object of this invention to provide a snapacting device which has a relatively large amount of snapmotion for its size.

A further object of this invention is the provision of a snap-acting device which for its size is relatively insensitive to dimensional tolerances, thus leading to ease of manufacture.

Yet another object of this invention is to provide a snap-acting electrical switch of miniature size which is relatively simple to manufacture, and simple to calibrate.

Other objects and advantages will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangement of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

Briefly stated, a snap-acting mechanism in accordance with the present invention comprises a blade of a flat, resilient material having outer and center legs extending in essentially the same direction from a juncture portion. The free ends of the outer legs are connected to a support by a pair of connections which are spaced so as to distort the outer legs toward one another, thus urging the center leg toward a position of relative equilibrium. One of the connections permits pivotal movement of its corre sponding leg, and means are provided for imparting pivotal movement to that leg so as to carry the center leg away from the aforesaid equilibrium position.

In the accompanying drawings, in which several of various embodiments of the invention are illustrated:

FIG. 1 is a plan view of a switch of this invention;

FIG. 2 is a plan view similar to FIG. l but with certain parts removed, to assist in seeing other structure;

FIG. 3 is a front view of a switch incorporating the FIG. l structure and also a casing or cover, and actuating 3,105,885- Patented Oct. 1, 1963 ICC means, parts of the casing being broken away to reveal details of structure;

FIG. 4 is a side-elevation of the FIG. 3 structure, again with parts of the casing broken away to reveal details of structure;

FIG. 5 is a bottom view of the FIG. l structure;

FIG. 6 is an enlarged view of an unstressed snap-acting blade used in the FIG. 1 structure;

FIG. 7 is an enlarged isometric view of an actuating arm used in the FIG. 1 embodiment;

FIG. 8 is a greatly enlarged fragmentary plan View of a portion of a mounting pin, the aforesaid actuating-arm, and snap-acting blade;

FIG. 9 is an enlarged view of a portion of the FIG. 3 structure (with some parts omitted for clarity) to illustrate the parts in one operating position;

FIG. 10 is a cross-section of the FIG. 9 device, taken in the direction of sight lines 10-10 thereon;

FIG. 1l is a view similar to FIG. 9, but showing the same parts in a second position;

FIG. l2 is a cross-section of the FIG. 11 device, taken in the direction of sight lines 12-12 thereon;

FIG. 13 is a view similar to FIG. 1, but showing a second embodiment of the invention; v

IG. 14 is a front view of the FIG. 13 embodiment an FIG. 15 is a simpliied representation of a switch in accordance with another embodiment of the invention.

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

In carrying out this invention, use is made of an element shown and described in United States Letters Patent No. 2,777,032, issued January 8, 1957, to which attention is directed for a full disclosure of its construction. For the purpose of this application, it will be suicient to describe the said element or blade briey as follows.

Turning to FIG. 6 ofthe drawings, the element or blade is indicated generally by numeral 2, and consists of a threelegged member having the outer legs 4 and 6 and the inner or middle leg 8. The outer legs 4 and 6 are joined to the middle leg 8 by means of the curved juncture portions 10 and 12. Openings are provided in the end of each of the outer legs 4 and 6. In the example shown, such openings are the mounting holes 14 and 16. Instead of holes, slots could be provided extending inwardly of each end from the outer edge thereof, since it is not necessary that there be a complete enclosure at the end `of each arm. What is needed for this embodiment is that VContacts 18 and 20 may be attached to leg 8 by riveting or welding, using well-known techniques.

As explained in the aforementioned patent, the blade is stressed -to make it snap-acting by mounting the blade in such `a manner that the ends of legs 4 yand 6 are forced toward each other. This causes the blade to 'adopta dished coniiguration, with the end of center leg 8 being moved out of the plane of the ends of legs 4 and 6. If the center arm is now pushed toward the plane of the outer legs, la position of instability will be reached, and further rmotion of the center leg in the same direction will cause the blade to change its Idirection of dishing -with a snap-action, thus throwing the end of leg 8 to the other side of the blade with a sn-ap-action. Utilizing the present invention, a lsnap-switch can Abe made in miniature size, and lat present such devices are being constructed in which the blade shown in FIG. 6 is made of y0.004 inch thick beryllium copper, `and is `0.192 inch long, and `0.208 'inch wide.

Referring now to FIGS. 1, 3 and 4 there is shown (enlarged by a ratio `of approximately 15:1) a plan view of a miniature switch incorporating the FIG. 6 blade. (in this drawing, -as in others, certain thicknesses of materials and other dimensions Iare not lscaled in proportion, the reason being the shading 4and other requirements of Patent Otlice drawings.) A base is provided comprising the metal ring 22 in which is fused the glass l-ler or electrically insulating header 24, terminals 26, 28 and 30 of electrically conducting metal passing through the glass and being fused thereto lwhile `being insulated from each other. The construction of the header plate and its terminals follows conventional practice, and is not a part of this invention.

As indicated above, terminal 26 extends through the header, and on its inner end is provided the enlarged shoulder or ange 32 and a neck 34. A switch support plate 36 of metal is provided and has therein a mounting hole 38 which is a squeeze tit onto neck 34, las shown. (If

desired, support plate 36 may lbe Welded to shoulder 32). Support plate 36 is provided with two other holes 40 and 42, as shown. A post 44 is provided which has at one end the reduced end portion 46 which is press-fitted into hole 40. Post 44 is made of metal and is hexagonal in crosssection to enable gripping it with a wrench for turning.

The other end of post 44 is provided with the neck portion 48. A flat-bottomed circular -groove 58 is provided, as shown, at the junction of neck 48 with body 44, andthe body 44 is cham-fered or relieved as shown at 52. Similarly the neck 48 is relieved by chamfer 54 `on the other side of groove 50.

Another post 56 is provided with a reduced end portion 58 which is squeeze-fitted into hole 42 in plate support 36. Similarly to post 44, post 56 is provided with a neck portion 60, and Ia dat-bottomed groove 62 like groove 50. Post 56 is relieved by the chamfers 64 and 66, similar to chamfers 52 and 54.

Neck 48 is formed on post 44 off-set from reduced portion 46. That is, neck 48 is axially offaset. Thus, when the post 44 is turned, neck 48 will be moved toward or away from neck 60.

Blade 2 is mounted on the posts 44 4and 56 by rotating post 44 until necks 48 and 68 are aligned with holes 14 and 16. The blade is then moved so that holes 14 and 16 receive necks 48 and 60. It will be noted that the position of posts 44 and 56 on support plate 36 is such as to permit the blade to be thus dropped over the necks in the unstressed state. Thereafter, with blade 2 in the vicinity of grooves 50 and 62, post 44 is turned in the support plate and neck 48 is thus moved closer to neck 60. This causes the iiat bottoms of grooves 50 and 62 to press against said inner rims to force leg 4 toward leg 6. In other words, the free ends of outer legs 4 and 6 -are connected to support 36 by a pair of connections which are spaced so as to distort the outer legs toward one another, thus urging the center leg toward a position of relative equilibrium.

At this point, an important Ifeature of the invention is to be noted, namely, that the engagement of the legs 4 and 6 by their respective posts is a pivotal one. That is, the legs are permitted to flex freely, both transverse to the leg and longitudinally of it. 'That is, each outer leg can twist about .an axis which extends in the same approximate direction as the leg. It is this freedom of Vexure which permits a new method of operation of the blade and which leads to many of the `advantages of the invention, such as ease of calibration, relative non-dependence onV critical dimensional tolerances, relative large"snapmotion, and the possibility of extreme miniaturization.

Switch support plate 36 is provided at its rear with the up-turned tab 68 (see FIG. 4) which serves to support one end of the actuating `arm 70. Referring to FIG. 7, the 'arm 70 is generally Y-shaped and comprises the leg portion 72 and the two side extensions 74 and 76.

. of the element.

Each of extensions 74 and 76 includes a down-turned tab 78 and 80, respectively. Each extension and a portion of its t-ab is pierced with one of the slots 82 and 84, as shown.V Slots 82 and 84 are large enough toiit freely over necks 48 and 60, respectively.V LActuating arm 70 is preferably stamped and formed from metal, but may, if preferred,

be molded from moldable plastic such as nylon or Teflon.

As shown in FIGS. 3 and 4, when the yarm 7 9 is mounted in place, the tabs '78 and 80 press, respectively, onthe outer edges of the ends of legs 4 and 6 adjacent the mounting holes .1;4 and 16. The arm 70 is held in this position by the engagement of slots 82 and 84 by necks 48 and 60, and by the end of leg 72 resting on the upper end of tab 68. While the end of leg 72 is shown, for simplicitys sake, as resting on the tab 68, it may be fastened to the tab in pivotal manner by any conventional means. Por example, a hole can be provided in the end of leg 72 to receive loosely a screw which in turn threads into the. up- K standing tab 68; or, the end of t-ab 68 may be provided with a narrow extension adapted to passthrough a hole in the end of leg 72 and be bent over at right'anglesl Such constructions are not shown in the drawings because Y they are clearly conventional and well-known in thefart.

As has been explained in connection with the descrip'- tion of the blade 2, the forcing of the ends of legs`4 and 6 toward each other will cause the blade to become somewhat dished, thus displacing the center leg 8 to oneside This dishing and displacement are clearly show-n in FIG. 3, where the center arm 8 is shown displaced downwardly. Because of the pivotal engagement of the arms by the necks and the resulting pivotal It will be noted in FIGS. 9 and 10 that the tabs 78 and 80 i If, now, the

press against these tilted sides of the legs. actuating :arm is pressed downwardly (-as drawn), the

free ends of the outer legs 4 `and 6 are rotated about the v attached to the upper (or inner) end of terminal 30 an L-shaped contact arm 86 with the overhanging end-portion S8. The bottom (as drawn) or inner face of end 88 has attached thereto the facing material 90' of electrical contact metal such as silver, to provide a mating contact surface for contact 18. The end 88 overhangs contact 18 as shown and is positioned to be engaged by the latter in one position of the center leg 8. The attachment of member 86 to terminal 36' is preferably by welding, butl may be by soldering, tlf desired, or brazing.

In like m-anner, an L-shaped contact arm `92 is fastened, i

as by welding, soldering `or brazing, to the upper V(as drawn) or inner end of terminal 28 l(see FIGS. 2 and 4).

The end portion 94 of arm 92 has agfaeing material 96 of electrical contact metal such as silver thereon, and the portion 94 with its facing material is positioned to lie underneath 'the snap-acting blade so that facing Y96 f will be engaged by contact 20 in one of :the positions of center leg 8.

As shown in FIGS. 3 and 4, la casing 100 is provided into fwhich snugly tits the metal ring -or flange 22. The

top 102 of casing 100 is depressed inwardly, as shown,`

anda hole N4 is provided at the center thereof which isk adapted to receive the flanged guide bushing 106. l Guide i bushing 186 is provided with a hole 108 which slidably receives the actuating pin 110. VA iiexible metal diaphragm closure member 112 having a surrounding ange V114 snugly envelopes the upper end of the casing 100.A l

This rotation will cause The center of the diaphragm is provided with a at portion, and on the outside thereof there is fastened (as by welding) the flat-bottomed actuating button 116. On the underside of the yaforesaid flat portion is fastened the flat welding cap 118. l(In manufacture, the diaphragm, actuating button and welding cap are assembled, in conventional manner, by a single welding operation.) The flange or rim 114 is soldered or seam-welded to the casing 162 to provide `a hermetically sealed closure for the upper end of casing 100. (Of course, the button 116, cap 118, and bushing 106 are all assembled in place prior to such closure operation.)

Pin 110 is inserted in hole 10S, and then the switch assembly (all as described earlier) is slid into the casing 100 as shown in lFIG. 3. Calibration of the device for pressure `and motion response is etfectuated by adjusting the longitudinal position of the switch assembly in the casing 1419. When the desired position is obtained, the ring 2 is seam-welded (or soldered) to the casing 100, thus providing a hermetic seal at the bottom of the casing.

With this construction, a hermetically sealed switch is obtained in which the casing 'and mounting parts -cooperate to provide adjustment.

yin operating, with the device set as shown in FIGS. 3 and 4, if the button 116 is pressed inwardly, the pin 110 will transfer this motion to the actuating arm 70. Depressing of the arm 70 depresses tabs 78 and 8l), which in turn exerts -a twisting motion or turning moment `of the ends of arms 4 and 16, as described above, about their respective fulcrum points, with the result that the center leg 8 will snap upward (as drawn) to bring contact 18 into engagement with facing 96 of contact end 88. Contact end 85 is positioned close enough to contact 18 so that center arm 8 cannot reach an upper equilibrium position. Thus, upon release of the actuating button 116, diaphragm 112 moves button 116 upwardly and the pin 116 and arm 72 are released. The outer legs 4 and 6' pivot-back toward their initial positions and the center leg 8 snaps back int-o the FIG. 3 position. For clarity as to the resulting motions, reference is directed to FIGS. 9 and l0 which show the center lleg V8 in lone position (contact 2i) engaging facing material 96), and FIGS. 1l and 12 show the center leg in the upper or snapped-over position (contact 18 engaging lfacing material v91)).

If desired, the end of leg 72 may be pivotally lfastened to the tab 68, and either (but not both) of tabs 78 `and 81') may be eliminated. Assuming, as an example, that tab 8l) is not used and that tab 78 continues to bear against the outer edge of the end of leg 4, motion of the actuating yarm 70 will serve to impart a twisting motion to leg 4 which will in turn cause the center leg to snap.

Referring now to FIGS. 13 and I14, there is shown another embodiment of the invention. In this embodiment of the invention the same principle of operation of the snap-acting blade is used, i.e., la mounting therefor which permits a rotation of the ends "of the outer arms, but differs as to where the fulcrum lies.

As in the previous embodiment, the ring 22, glass header 24, and terminals 26, 28, and 30 are provided. The shoulder 32, neck 3'4, and switch support plate 36 are also provided. The upper contact arm 86, lower Contact arm 92 are likewise provided and are attached, as before, to their respective terminals 30 and 28.

In this instance, however, the snap-acting element 120 is mounted by the outside edges 122 and 124 of the side arms 126 and 12S. The mounting is accomplished in the mounting bar 131i which lies across the support plate 36 at one end thereof and is attached thereto as by welding. Bar 1311 is of metal and has attached at each end thereof the npturned legs -132 and 134. Each of legs 132 and 134 has formed across its inside face the V-groove 136 and 13S, respectively. The outer edge of the end of each side arm is provided with a `frat-bottomed notch 1441 and 142, respectively, each of which notches straddles its respective mounting leg 132- and 134 to prevent longitudinal motion of the `snap-element. When mounted, the llat bottoms 144 and 146 of the said notches engage the V-grooves 136 and 1318, respectively. It will be noted that the notches 146 and 142 may be so deep, if desired, that portions of the edges of ends 122 and 124 may extend laterally vbeyond the support legs '132 and 134. In such a construction, the blade may then be actuated by pushing on these outer edge portions (as in the previous embodiment) or 4on the inside (as in this embodiment) An actuating bar 148 is provided having at yone end thereof the down-turned tabs or legs 1511 and 152. Each of these legs is charnfered to a knife-edge, and, as can be clearly seen in FIG. 14, bears against the outer legs 126 and 128 but adjacent the inner edges thereof. A clevis 154 is provided at this end of the bar 148 to provide electrical clearance between bar 148` and contact arm S6, if necessary, when the arm is depressed.

The `other end 156 of arm 148 rests on top of an upturned leg 158 which is attached to support plate 36. The leg or tab 158 is made wider in this instance, than in the previous embodiment, and a pair of pins `160 and 162 pass through suitable holes in end 156 and into leg 15S, these pins serving to keep the end 156 of the arm from sliding or :swinging horizontally on leg 15S, and thns serve to orient the actuating arm with respect tolegs 126 and 128` of the snap-acting element. The t of pins 1611 and 162 in their respective holes is such as to permit the arm to rock slightly about leg 158.

A center leg 164 is provided for blade 1211 (corresponding to center leg S of blade 2) and is provided at its end with contacts 166 and 168, which correspond to contacts 18 and 2l).

A push pin 11h is provided, as in the previous embodiment, and bears against the actuating arm 148 as shown.

This second embodiment is fastened in a casing alike in all respects to the previous casing 106; thu-s providing a hermetically sealed enclosure for the switch parts.

In operation, and referring to the parts positioned as shown in FIG. 14, when the pin 110 is pushed downwardly, arm 148 is depressed, which in turn causes legs or tabs 1511-152 to depress the inner edge of side arms 126 and 128 about the fulcrum points provided by V-grooves 136 and r138. This rotation about the `tiulcrum points will cause the center leg 164 to snap downwardly, as drawn, and cause contact 168 to engage con'- tact arm 92--94 while opening the electrical connection between contact .166 and contact arm 38.' Release of push pin will permit .the reverse motion of the parts.

It is to be noted that the initial bowing of the outer,

legs 126 and 12S inwardly toward each other is accomplished, in this instance, by mechanically bending the side legs 132-134 toward each other.

It is to be noted that there is a difference between the operation of the iFIG. 1-12 embodiment, and that of FIG. 13-14, in regard to the relationship between the motion of the actuating arm in each case and the center leg.

In the FIG. .l-l2 embodiment, the actuating arm moves in a direction yopposite to the eventual snap-motion of the of the FIG. 1-l2 embodiment than will be the case forl the FIG. 13-14 embodiment. f

In View of the above, it will be seen that the several objects of the invention are achieved and other advann tageous results attained. Y

In the embodiment 'of the invention illustrated in FIG. l5, blade'Z has its outer leg 6 pivotally connected to support 36 by the edge of hole 16 engaging the chamv fened recess 62, as in the embodiment of FIGS. 1-12. The free end of outer leg 4 is liked in position relative to support 36 by being secured to the upper end of a metal post 180 by welding or soldering or by riveting, as shown. Thus a portion of post 180 of reduced diameter passes through hole 14 and its upper end is upset or deformed to form rivet head 181. Rivet 131 clamps the end of leg 4 to the upper surface of the post and the post is xed to the support 36. The spacing between recess 62 of post 56 :and the body of rivet 181 is' selected so that the legs 4 and v6 are deformed toward one another and center leg S is urged .toward a downward equilibrium position so that contact 20 engages `Contact surface 96.

By means of an electrical connection to post 180, the embodiment of the invention shown in FIG. 15 features improved electrical contact to the blade 2.

To actuate the snap-acting device just described, an actuator rod 182 is slidably supported in a guide 133. It has a control button 184 at its upper end and its lower end 185 is positioned to engage an outer, upper surface portion of outer leg 6. Thus, by ydepressing button 184, leg 6 is pivoted and in a snap-action, center leg 8 is carried away lfrom the position shown in FIG. `15 and contact button engages contact surface 90. With member S8 positioned as shown, when control button is released, the blade 2 returns to its initial condition in a snap action.

Of course, actuation of the blade in `the embodiments of FIGS. l-l2 and 13-l4 can be acomplished by producing pivotal movement of only a single leg. An actuator of the general type illustrated in FIG. l5 may be employed. f

As explained in connection with the embodiment of FIGS. l-l2, contact lS8 is positioned so that only a single equilibrium state (downward) is provided for center leg 8 and this is also shown in FIG. 15. The same result can be achieved by constructing post 18) with its upper surface at an appropriate angle, such as represented by broken line #186. While the angle illustrated provides a single equilibrium state in a downward direction, an opposite angle will obviously effect a single upper equilibrium state.

Obviously, in any of the embodiments of the invention which have been illustrated and described, the upper and lower contacts may be appropriately positioned so that the center leg 8 is urged toward upper and lower equilibrium positions. For such applications, means are provided for actuating the vblade from each position whereupon 'its goes into the other position with a snap action. For example in FlG. l5, upper contact l88 may be raised and an actuator assembly like the one designated by numerals 182-185 is positioned below leg 6 to effect pivotal movement in the opposite direction.

As many changes could be made in the above constructions without departingffrom the scope of the invention, it is intended that all matter conta-ined in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is: t

1. A snap-acting mechanism comprising a support, la resilient normally filat blade having spaced-apart outer legs and a center leg joined thereto by one end and extend ing therebetween, means attaching said outer legs to said support including a pair of upright posts for said outer legs, one of said posts being provided with a groove therein and the end of 4a corresponding one of said outer legs having an edge engaging said `groove in pivotal connection therewith, the other of said posts constraining movement of the remaining outer leg in a direction away from said one post, said one post being movable at least in part in said direction toward an adjustably-frxed position wherein said posts are spaced apart a distance such Vas to distort the blade and thereby cause saidcenter leg'to snap across a position of unstable equilibrium, `and yactuating means adapted to engage said blade and impart pivotal movement to the end of said one outer leg.

2. A snap-acting mechanism according to claim 1 in which said other post has a groove therein and the end of` the corresponding outer leg has an edge engaging said groove in said other post in pivotal connection therewith.

3. AV snap-acting mechanism according to claim l in which the end of said other outer leg is secured at an angle relative to a line extending between said ends of said outer legs.

4. A snap-acting mechanism according to claim 1 iurther comprising an electrical contact carried by the free end of said center leg and another electrical contactV mounted on said support yfor engagement with said firstmentioned contact, and means for completing electrical circuit connections to said contacts. Y

5. The snap-acting mechanism of claim l in which said actuating means comprises an elongated member having a leg portion and side extensions having means thereon adapted to engage each of the said outer legs to twist said outer legs about an axis.

6. The snap-acting mechanism of claim 1 in which said actuating lmeans comprises an elongated member having a center leg and side extensions attached thereto, eaohof said side extensions having 'at its end'a tab at anangle n thereto, each tab engaging one of said ends near the edge thereof and being adapted to move said edge :pivotallyA about the respective support.

7. A snap-acting .mechanism comprising a support, 'a' resilient normally `flat blade having spaced-apart outer legsV and ia center leg joined thereto by one end and extending therebetween, means for attaching said blade to said support comprising a pair of spaced-apart posts, the ends of said'outer legs being provided with holes adapted to -iit loosely over said posts, each of said posts being pro.-y vided with a groove receiving therein a portion of the rim of the respective hole, one of said posts being movable at least in part toward the other of said posts to an adjustably fixed position wherein saidv posts are spaced apart a distance such Ias to strain said outer legsabnorfmally toward each other to distort said bladeinto a dished shape, a third support post, and an actuating arm `for snapping said blade, said ar-rn comprising an elongatedY center leg and two side extensions attached to one end thereof, each of said side extensions having a hole at itsV other end and a tab beyond said hole, each tab extendin-g outwardly therefrom at lan angle and thereto, said holes fitting over said posts and saidV tabs bearing against the outer edges of said actuating arm resting on said third support.

8. A snap-acting mechanism comprising a support, a` resilient normally iiat blade having spaced-apart outer legs and a center leg joined thereto by one end and extending therebetween, means for attaching said blade to said support comprising a pair of spaced-apart posts, the Youter edges `of the ends of said outer legs being provided with notched portions, each of said posts on its inner side being provided ywith a transverse groove receiving therein said notched portions, one of said posts being movable at least in part toward the other of said posts to an iadjustablyj fixed position wherein said posts are spaced apart a dis-V tance such as to strain said outer legs abnormally toward each other to distort said blade into Ia dished shape, a third support post, and an actuating arm for snapping said blade, said arm comprising an elongated center legk and two side extension legs attached to one -end thereof, each of said side extensions having atV its end thereof ,a

tab extending outwardly therefrom at an angle thereto, said tabs engaging the ends of said outer legs adjacent the inner edges thereof, and means holding. andgurdrng the other end of said .actuating arm on said third support.

9. A snap-acting mechanism comprising a support, a resilient normally flat 4blade having spaced-apart outerlegs and a center leg joined'thereto by one end and extending therebetween, said support including a pair of upright posts, veaohpost comprising a body portion and a neck portion of reduced diameter, each of said outer legs being provided with a hole adjacent its end and iittingrloosely over one of said neck portions, one of said posts being stationary and the other of said posts being movable toward and -adjustably fix-ed position to bring its neck portion toward and away `from the other neck portion, said movable post being positionable to strain said outer legs toward one another to dish said blade, and actuating means for engaging an end portion of one of said outer legs to tilt said end portion on the corresponding neck portion.

10. The snapactng mechanism of claim 9 in which l said other post is provided with .another neck portion of reduced diameter, one of said neck portions being engaged by and rotatable in said support, the other of said neck portions being engaged by the rim of one of said holes,

References Cited in the tile of this patent UNITED STATES PATENTS 2,624,819 Spina Jan. 6, 1953 2,777,032 Burch Jan. 8, 1957 0 2,825,785 Taylor Mar. 4, 1958 FOREIGN PATENTS 622,781 Great Britain May 6, 1949 774,911 Great Britain May 15, 1957 

1. A SNAP-ACTING MECHANISM COMPRISING A SUPPORT, A RESILIENT NORMALLY FLAT BLADE HAVING SPACED-APART OUTER LEGS AND A CENTER LEG JOINED THERETO BY ONE END EXTENDING THEREBETWEEN, MEANS ATTACHING OUTER LEGS TO SAID SUPPORT INCLUDING A PAIR OF UPRIGHT POSTS FOR SAID OUTER LEGS, ONE OF SAID POSTS BEING PROVIDED WITH A GROOVE THEREIN AND THE END OF A CORRESPONDING ONE OF SAID OUTER LEGS HAVING AN EDGE ENGAGING SAID GROOVE IN PIVOTAL CONNECTION THEREWITH, THE OTHER OF SAID POSTS CONSTRAINING MOVEMENT OF THE REMAINING OUTER LEG IN A DIRECTION AWAY FROM SAID ONE POST, SAID ONE POST BEING MOVABLE AT LEAST IN PART IN SAID DIRECTION TOWARD AN ADJUSTABLY-FIXED POSITION WHEREIN SAID POSTS ARE SPACED APART A DISTANCE SUCH AS TO DISTORT THE BLADE AND THEREBY CAUSE SAID OUTER LEG TO SNAP ACROSS A POSITION OF UNSTABLE EQUILIBRIUM, AND ACTUATING MEANS ADAPTED TO ENGAGE SAID BLADE AND IMPART PIVOTAL MOVEMENT TO THE END OF SAID ONE OUTER LEG. 